1. Field of the Invention
The field of the invention is to a fluid lock, and method, for permitting transiting an object, such as a human being, between different fluid pressures, wherein the fluid lock may, for example, be:
(1) An air lock in a space shuttle, space orbiter or space station (each sometimes herein called generically a spacecraft); or
(2) A waterlock in a submarine, or other submergeable craft,
for permitting a human being therein to leave the craft in an enclosing suit, such as a space suit (sometimes called herein an EMU, or extra vehicular mobility unit); and to move through the surrounding fluid (whether it be in space, air, or water) outside the craft in extra vehicular activity (sometimes called herein an EVA).
2. Description of the Related Prior Art
Existing devices are known as air locks, for transiting (such as in air, in space or underwater) from one pressure to a different pressure, such as the low pressure or vacuum of space. Their design has not changed fundamentally since their first use during the construction of the initial underwater subway tunnels in the 19th century. Current designs require the user to either vent the gas from the higher pressure side, or to pump it into storage until ready for repressurization.
Prior art air lock 10 in FIGS. 1 and 2 is now used in existing space orbiter 11 of a space shuttle, and is planned to be used for a space station.
Here are some of the problems in such prior art air locks, which problems are solved by this invention.
Substantial problems arise from suiting up two crew members in air lock 10, located in spacecraft 11 cabin 18. That requires that there be room for two crew members and a helper to simultaneously occupy air lock 10, and for added installed equipment in FIG. 2, such as lighting, space suits 12 and their storage racks 13, ventilation 14, hatch 15 to cabin and hatch 16 to cargo bay 17, foot restraints, and the suit systems checkout console. There are also provisions in air lock 10 for vehicle life support systems or suit servicing panel 20 (supplying oxygen, cooling, communications, etc. during pre-breathing) to be attached to each suit so that suit oxygen supplies and batteries will not be used up while the crew members are going through the procedures prior to exiting air lock 10 into the vacuum of space.
More problems are added by traveling through the existing lock 10, and arise not only from the long time required to prepare for, and to, travel through the air lock, but also the large gas or air volume that must be handled by venting, or by pumping and/or storing.
A long time is required to travel through air lock 10. Two crew members enter air lock 10 through cabin hatch 15 along with a third person to help them donn their flexible suits 12. The process of suiting up can take as long as three quarters of an hour, after which the third person exits air lock 10 through cabin hatch 15 to cabin 18. The two suited crew members attach umbilical air hoses and electrical connectors to the outlets built in air lock 10 panel 20 and prepare to wait out three one-half hours of "pre-breathe" time to reduce the amount of nitrogen in their tissues before going onto their EVAs. This is necessary because (1) spacecraft 11 pressure (normally at sea level at 14.7 psi absolute) and flexible suit 12 pressure in space differ greatly, and (2) the nitrogen dissolved in the blood and fatty tissue would otherwise come out of solution during an EVA, producing localized blockage of blood flow, discomfort, and possibly death.
After finishing "pre-breathe", the crew members can disconnect their suits from the spacecraft systems panel 20 and go on internal suit power, complete pre-EVA suit checks and begin to depressurize air lock 10. The gas in air lock 10 is vented in a few minutes. and after final suit integrity checks, the two suited crew members are ready to open outer hatch 16 and egress to cargo bay 17 and to space. On a space station, an additional ten minutes may be required to pump down air lock 10.
The reentry procedures to spacecraft 11 are the reverse of the above, but omit the suit integrity checks.
Handling a large volume of gas in air lock 10 creates problems, whether the gas volume handling be by venting, or by pumping, resupplying, and/or storing.
Venting gases from air lock 10 into space is undesirable because of the contaminants that are carried with the gases, such as water vapor, hair, skin flakes, etc. Cold optical surfaces on the outside of spacecraft 11, for example, will be become coated when contacted by these gases.
The expected large number of EVAs from a space station creates large, potential, logistic costs for resupplying or replacing expended gases lost. Each air lock 10 operation requires pumping air lock 10 down to 2 psi absolute within ten minutes prior to each egress. That requires the installation of a 5 kilowatt pump weighing 300 lbs and over three and one-half feet long for each air lock on a space station. Time to pump down would be in addition to the three one-half hours of "pre-breathe" time mentioned above as required to reduce the nitrogen in the blood stream of the crew members, in order to reduce the probability of "bends" (decompression sickness), which can result if pressure drop exceeds about 5 psi from the initial pressure of 14.7 psi absolute (one atmosphere).
The reduction in vented gas volume in air locks 40, 140 in the present invention will essentially eliminate contamination of cargo bay equipment and will almost eliminate logistic costs associated with resupplying of gases to a space station.
When a suited crew member leaves a spacecraft and travels through space, this is called an extra vehicular space activity or an EVA.
A three (3) EVA limitation is imposed by the limited amount of life support gases available to the crew for repressurizing air lock 10 in space orbiter 11, which gases are vented and lost every time someone exits air lock 10 to perform an EVA from orbiter 11. The limited power and volume available on board orbiter 11 preclude adding a pumping system which could reduce a loss of gases.
Space orbiter 11 depends upon the EVA crew to assure that its cargo bay doors 29 are closed, specially if its remotely operated door actuators should fail to function. This requires that the crew members be prepared to perform and EVA late in the mission, just before reentry, to manually close the doors. This contingency requirement uses up one of the three possible EVAs allowed on a given orbiter 11 flight.
The three EVA limitation, and the long time required to suit up, and to prepare for going, and to go, through air lock 10 force the crew members to remain outside in space for seven (7) hours at a stretch, and carry with them their food to eat and defecating equipment.
More problems are added by the large weight and volume of air lock 10.
Air lock 10 is large enough to just accommodate three people. This is necessitated by the frequent dependence of the two EVA crew members on help from a third party in the donning and checkout of their space suits or EMUs 12. The resulting size of air lock 10, and the necessity for it to sustain a pressure differential of up to a full atmosphere, results in a subsystem which weighs about 1800 lbs and occupies about a one fourth of the available void volume in orbiter 11 cabin 12 mid-deck. In addition, air lock 10 must be equipped with lighting, ventilation, communication, umbilical and electrical connections, and storage racks for the EMUs and other auxiliary equipment. Much of that equipment, such as for lighting and communications, is redundant to what already exists in the mid-deck area, but must be duplicated because of the long isolation of the crew members inside large air lock 10.
The presence of all that mass of air lock 10 in the mid-deck, in a relatively forward location relative to the center of gravity of orbiter 11, contributes to center of gravity limitations, which require the aft location of payloads, such as in space lab 27 in FIG. 3. That aft location, in turn, requires long tunnel 28 between air lock 10, cargo bay hatch 16 and space lab 27, and requires additional outlet hatch 19 for emerging from tunnel 28 into space.